Marine Species Identification Portal : Paddler crab

Hwang & Takeda, 1986

Diagnosis: Carapace squarish, glabrous and evenly convex in both directions, its general appearance being markedly close to that of Varuna litterata (Fabricius). First male pleopod divided into two lobes of unequal size at its tip as usual, but the larger lobe subdivided into two by a deep cleft and fringed with sinuous, chitinized brown ridge.

Description: Carapace squarish and almost glabrous, only with some minute pits along cervical groove, being evenly convex in both directions; protogastric and mesogastric regions are jointed to form a lobe curved down to frontal margin; hepatic and epibranchial regions are in conformity on the general convexity of carapace, being only slightly depressed in their lateral parts; cervical groove with a H-shaped mark in the middle, and indistinct in its lateral part; subregions of branchial region not distinct, only with very shallow, lateral grooves; cardiac region forms a distinct convexity between branchial regions of both sides, extending backward to intestinal region, from which it is separated laterally by a short and shallow sulcus at each side.
Front horizontal and broad. Upper orbital margin fissured and very weakly everted; its inner angle slightly deflexed. Antero-lateral border of carapace cut into three lobes by two small notches; first lobe confluent with external orbital angle, its margin being nearly truncated; second lobe only slightly shorter than the first and weakly convex; the third is small and nearly longitudinal or rather convergent. Postero-lateral part of carapace is marked by a facet delimited from branchial region by a linear ridge originated from posterior end of third antero-lateral lobe to posterior end of postero-lateral border of carapace.
Buccal cavern squarish, a rhomboidal gap being left between third maxillipeds of both sides. Merus of third maxilliped auriculated at its external angle; exopod narrower than ischium.
Both chelipeds similar in shape and equal in size, length being proportional to size of carapace; female chelipeds are smaller than males' as usual, but not remarkably so. Carpus with a sharp tubercle at its inner angle and usually with two small ones on each side, being fringed with soft hairs on inner upper margin. Tip of fingers not spoon-shaped, but slightly curved inward; a very narrow gape between cutting eges of fingers.
Ambulatory legs long and flattened, being thickly fringed with hairs on both margins of distal two segments. Breadth of merus is about 0.35 times its own length, and dactylus about 0.6 times the length of merus.
Male and female abdomens are as figured. Female abdomen is somewhat tongue-shaped, with obtuse, triangular distal segment.
Male first pleopod heavily calcified as usual; its distal part densely provided with stiff setae and divided into two lobes of quite unequal size; larger lobe deeply cleft at the middle, distal margin between two lobules thus formed being fringed with a sinous, chitinized brown ridge; a genital orifice at the tip of inner lobe surrounded by protruded soft ridge. (Hwang & Takeda, 1986)

Type locality: Da-Taung village, I-Lan County, Taiwan.
Range: Japan - Sakawa-gawa, Kanagawa Prefecture (Chokki & Ishihara, 1987); Taiwan - I-Lan County (Hwang & Takeda, 1986); Hong Kong (Davie, 1992); Philippines - Cebu (Hwang & Takeda, 1986).

Images

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V. yui M

Paddler crab (Varuna yui)